Posted on 27-May-2005 17:24 by Peter Torr Smith|
Filed under: Reviews
This month I had the opportunity look at 3 GPS units from www.efrontier.co.nz. Intergen was hosting this month’s Windows Mobile User Group in Wellington, and for it had put up some great spot prizes, including the GlobalSat SD-501 SDIO GPS receiver. eFrontier also lent me demo units of the Leadtek 9534 Compact Flash GPS receiver and the latest GlobalSat Bluetooth GPS receiver, the BT-338. All three utilise GPS Chipsets from www.sirf.com, though each use a different one.
This unit initially appealed to me because of its robustness. I like Compact Flash as a Pocket PC interface as it not only allows for a more solid device connection, but it grips onto the card or device more securely. The other appeal with this unit is the price. At NZ$140+GST (US$99), and with the supplied GPSWizard software, it’s a low cost way to get reasonably good GPS capability for you Compact Flash compatible Pocket PC.
The unit has no fiddly antenna fold-outs, and sticks out only what would seem reasonable to be effective. It almost felt like part of the Pocket PC when inserted. It has an RF socket for connecting an external antenna, unfortunately I did not have one that would fit so could not see what it is fully capable of (RF Connectors/plugs for external GPS antenna can vary so check before buying).
It unfortunately does not have any LED indicators for operational or fix status, and whilst it was 100% reliable when inserted, some visual feedback would have been rassuring. It uses an earlier generation of SiRF chipsets, and whilst the manufacturer states it uses the SiRFStarII chipset, it does not state which version. It probably uses LP, or low power, version, meaning a compromise in processing power. I also assume that it does not utilise SiRF’s XTrac technology.
My first outdoor play with using this unit was with my older HP iPAP h3860 Pocket PC using a Compact Flash expansion sleeve on a trip over to the Kapiti Island bird sanctuary. With GPSWizard I managed to monitor my location, speed, direction, and altitude at various points, though in very dense mountainous bush establishing a fix was not always possible.
I had to soft-reset the HP iPAQ h3860 almost routinely due to what turned out to be issues with GPSWizard, and not the hardware. The software would freeze after running for long periods (20 mins!) and did not respond well to the Pocket PC being turned on and off. This and my wish to conserve battery power meant I didn’t record our entire 6 hour adventure to the top. So either side of ons and offs and soft resets I did manage to take a couple of altitude readings from the cloud covered summit of Kapiti which placed it at 546M, at least 20M above that showing on most maps.
Not keeping the GPS unit switched on doesn’t give the chipset a chance to refine and optimize and track weaker sattelite signals. A rechargeable battery onboard would be an improvement, giving the ability to leave the GPS unit on and tracking even when your PDA device is switched off. The unit is stated to use about 110mA of power, so not too draining on batteries, but still could reduce PDA operating times by up to 25% since the PDA needs to be on to power the card device.
The next day I took this unit out for an urban road test alongside the Globalsat Bluetooth GPS receiver to see how they compared. For this I used my HP iPaq hx4700 and a trial copy of OziMap for VGA Pocket PCs. Without any NZ maps, I managed to source a scanned JPEG of a Wellington street map and get it roughly registered to work inside OziMap for the road-test.
In side by side comparisons, the Leadteak CF 9534 did not give as accurate or quick a fix as the BT-338, however it did do a pretty good job, and at half the price at that. In open spaces it works great. When surrounded by small to medium height concrete buildings, a weak fix was generally found after a few minutes (staying stationary seemed to help). And once it had a fix, it managed to maintain a variably, but acceptably, accurate track on my movements through a mixture of urban, residential, and coastal locations, most of which was quite hilly.
The fix does jump around a bit, sometimes a lot, in poor or reflective signal environments, but the average is generally pretty good. It lost track as one would expect going through the Mt. Victoria tunnel, but happily regained a fix within a couple of seconds of exiting the tunnel.
Road Test of BT-338 and CF-9534:
My walk to work into the high-rises of The Terrace
The entire “road test” – the left/west half with the BT-338, the right/east half with the CF-9534
Switchover from the BT-338 (left) to the CF 9534 (right). Note fix variation with 9534 when stationary around tall buildings, at least when getting its initial fix
Keeps a fix, though against the cliff, the signal seemed to be out a bit
The CF-9534 regained a fix on exiting the Mt. Victoria tunnel
Switch back to the BT-338. The CF- 9534 kept a loose track on my circuit around the Basin Reserve, the BT-338 much tighter
The Leadtek 9534 tracking loosely, though acceptably during a slow trip through the after work traffic
I did give this CF GPS unit a quick side-by-side comparision with a work colleague’s older dedicated handheld Garmin GPS device. Whilst by no means a scientific comparison, it appeared to me that this little CF unit gained a fix quicker, in poorer environments than the dedicated unit. So it certainly holds its own.
This receiver came with a mini CD with lots of PDF manuals as well as drivers for older Windows and CE devices, and a copy of version 1.0 of HiMark’s slightly awkward GPS Analysis Tool for Windows for viewing and analyzing GPS data and logs.
Overall, a small, robust, and well priced unit, quick to give a position in open spaces, but not as quick/accurate in poor signal environmnents. Great value for money for what it can do.
Small solid profile.
Useful for older PDAs that only have CF.
External antenna connector.
No need to keep charged – uses host power.
Uses up CF slot which may be required for a memory card.
No onboard memory.
No onboard battery.
Uses host power – reduce operational time.
A bit slower to get a fix in poor/reflective signal areas.
Not so good in urban canyon.